Reversible phase transformation of MnO2 nanosheets in an electrochemical capacitor investigated by in situ Raman spectroscopy

The reversible phase transformation is reported from hexagonal to monoclinic structure responding to the intercalation/deintercalation of Na+ between MnO2 nanosheets upon potential cycling in aqueous electrolyte via an in situ Raman technique. This structural evolution will influence the Na+ diffusion process in MnO2 nanosheets and cause phase retention during the self-discharge process.